Volatile anesthetics produce a balanced anesthesia by acting on a number of neural systems. While early studies attributed this array of actions to a nonspecific fluidization of phospholipid membranes, more recent work has pointed to specific actions of anesthetics on ion channels. Selective blockade of NMDA- sensitive glutamate receptors by volatile anesthetics has been linked to their amnesic, analgesic, hypnotic and neuroprotective action. Recent work by our laboratory and others has shown that both volatile anesthetics and n-alcohols have differing effects on NMDA-receptor function depending on the brain area studied. Further, we have preliminary data showing that the effects of volatile anesthetics on the NMDA receptor are influenced by the presence of the exon-5 splice in the NMDAR-1 subunit the receptor. The proposed studies will examine the effect of various volatile anesthetics on the electrophysiological properties of native NMDA receptors in rat brain and correlate those effects with the subunit composition of the receptors using single-cell RT-PCR. Specific Aim I will use whole-cell patch recording of NMDA- induced currents from acutely dissociated neurons and neurons maintained in primary culture to examine the effect of isoflurane on NMDA receptor function. Following recording of the NMDA- mediated currents, cytoplasm will be extracted from individual cells to analyze the mRNAs for NMDA receptor subunits present in each cell. This specific aim will extend our preliminary data linking the presence of the exon-5 splice to increased anesthetic potency and extend this work to other NMDAR-1 and NMDAR-2 isoforms. This aim will test the hypothesis that the effect of isoflurane on NMDA receptor function depends upon the subunit composition of that receptor. Specific Aim II will compare the effects of ethyl ether, isoflurane, enflurane, halothane and chloral hydrate on whole- cell currents elicited by NMDA and correlate those responses with the presence or absence of specific NMDA receptor subunit mRNAs. This specific aim will test the hypothesis that volatile anesthetics share a common dependence on subunit composition. Specific Aim III will examine the effect of volatile anesthetics on NMDA receptors expressed in HEK-293 cells transfected with combinations of NMDA receptor subunits found to influence anesthetic potency in native receptors. This Aim will verify experimentally, the correlational data from Specific Aims I and II.